A vertical axis clothes washing machine includes a tub containing a basket having an oscillating agitator to wash clothes placed therein. The tub is mounted by a suspension typically including springs and dampers.
During operation of the washing machine, an unbalanced load of clothes or other articles may cause the basket to spin or rotate off-axis and may cause the tub containing the basket to vibrate. The vibration excursions tend to be especially acute during the start of the spin cycle. At the beginning of the spin cycle, the excursions may become large enough, as the machine passes through resonance of the suspension, for the tub to bang against the washer housing. As the washer spin cycle progresses, the rotational speed of the basket increases, and the excursions tend to be limited at speeds beyond the resonance of the suspension.
Stiffening the suspension will keep the tub aligned, but permanently stiffening the suspension will increase the suspension frequency causing the machine to pass through resonance at a higher, more damaging speed. Accordingly, it will be appreciated that it would be highly desirable to temporarily stiffen the washer suspension to keep the tub aligned without permanently increasing the stiffness of the suspension.
Furthermore, typical suspensions require many parts which are expensive to manufacture. A typical damper includes a housing and piston therein which are separately manufactured components, and are also subject to friction wear during operation.
It is therefore also desirable to have a relatively simple and inexpensive suspension with few components.